The goal of this research project is to determine the relationship between chemically induced peripheral neuropathy and changes in the ionic characteristics and electrical excitability of the nerve membrane. Two methods are proposed to examine membrane excitability: extracellular recording of the rat sciatic nerve compound action potential and the double sucrose gap technique for recording the action potential and resting membrane potential of the rat sciatic nerve. Prior to examination of the nerve the rats will be exposed to either trichlorfon, n-hexane, trichloroethylene (each of which produces a peripheral neuropathy), parathion or toluene (which are both neurotoxic but do not produce a neuropathy). The effects on membrane excitability will be compared to data on the behavioral and histologic changes induced by the same agents over the same time course of exposure. The results of these experiments will demonstrate the extent of electrophysiologic changes accompanying nerve damage following exposure to neurotoxic agents. In the past, the electrophysiologic aspect of neurotoxicology has only rarely been utilized, compared with other neurotoxicity methodology. Yet, the technology is available with these methods to study the mechanism of action of neurotoxic agents at the level of the excitable membrane and its ionic channels. This type of information will be useful in determining the degree of long term risk imposed by neurotoxic agents and the course of treatment which might be most effective.